您需要将其绑定到构造函数，并记住对构造函数的更改需要重新启动服务器。否则，您将以相同的错误结束。

你不需要绑定任何东西，只需要像这样使用箭头函数:

class Counter extends React.Component {
    constructor(props) {
        super(props);

        this.state = {
            count: 1
        };

    }
    //ARROW FUNCTION
    delta = () => {
        this.setState({
            count: this.state.count++
        });
    }

    render() {
        return (
            <div>
                <h1>{this.state.count}</h1>
                <button onClick={this.delta}>+</button>
            </div>
        );
    }
}

虽然这个问题已经有了答案，但我还是想分享一下我的答案，希望对大家有所帮助:

/* 
 * The root cause is method doesn't in the App's context 
 * so that it can't access other attributes of "this".
 * Below are few ways to define App's method property
 */
class App extends React.Component {
  constructor() {
     this.sayHi = 'hello';
     // create method inside constructor, context = this
     this.method = ()=> {  console.log(this.sayHi) };

     // bind method1 in constructor into context 'this'
     this.method1 = this.method.bind(this)
  }

  // method1 was defined here
  method1() {
      console.log(this.sayHi);
  }

  // create method property by arrow function. I recommend this.
  method2 = () => {
      console.log(this.sayHi);
  }
   render() {
   //....
   }
}

检查状态 检查状态是否创建特定属性

这一点。状态= { 名称:", 电子邮件:”“ ｝ this.setState(() => ({ Comments: Comments //注释状态不可用 }))

2.检查(这个) 如果你在任何函数(即handleChange)中执行setState，检查函数是否绑定到这个函数或函数应该是箭头函数。

## 3种方法绑定到下面的函数##

//3 ways for binding this to the below function handleNameChange(e) { this.setState(() => ({ name })) } // 1.Bind while callling function onChange={this.handleNameChange.bind(this)} //2.make it as arrow function handleNameChange((e)=> { this.setState(() => ({ name })) }) //3.Bind in constuctor constructor(props) { super(props) this.state = { name: "", email: "" } this.handleNameChange = this.handleNameChange.bind(this) }

只需要更改bind语句 = > this.delta = this.delta.bind(this);

这是因为这个没有和这个绑定。

为了绑定，在构造函数中设置this.delta = this.delta.bind(this):

constructor(props) {
    super(props);

    this.state = {
        count : 1
    };

    this.delta = this.delta.bind(this);
}

目前，您正在调用bind。但是bind返回一个绑定函数。您需要将函数设置为其绑定值。